Park County · Alluvial and Sedimentary Rock Aquifers / Fractured Bedrock

Well Water in Park County, Colorado

Park County's mountain communities sit in South Park — a high-altitude basin with a long mining history. The Fairplay Mining District alone has over 18,000 mining claims on record. That legacy means heavy metals in the soil, tailings piles along waterways, and the potential for mining-related contaminants in groundwater. On top of that, recent PFAS testing found contamination in more than half the wells tested in one community.

Hardness: Variable

240 fttypical depth drilled (middle half 140–380 ft)

100 fttypical depth to water when drilled

6 gal/mintypical pump-test yield

14,454household wells on the state's records here

Typical (median) depth of household wells completed in each period, drawn to scale; the dashed outline reaches the depth that the deeper quarter of wells go past. Blue is where water stood when the wells were finished, where enough records give it. The rock pattern is a sketch of this area's ground, not a log of any one well.

What tested wells showed

Uranium limit 30 µg/L3% of 31 tests over the limit

Arsenic limit 10 µg/L1% of 119 tests over the limit

Nitrate limit 10 mg/L14% of 126 tests over the limit

Bacteria limit any coliform11% of 100 tests over the limit

Park County, CDPHE private-well lab results 2011–2020. People usually test because they have a reason to, so these rates describe tested wells, not every well. Bacteria counts any coliform detected.

What to test for and where →

503 permits here are for wells that replaced an earlier well. Wells get replaced when they fail, run dry or are re-drilled deeper, among other reasons.

Every well on record around Park County

Depth drilledunder 100 ft100–200200–400400–700700 ft +

A random sample of up to 2,500 household wells from the state's permit records, placed by their recorded location and coloured by how deep each was drilled. Locations on permits are often approximate, sometimes only to a section, quarter-section or 40-acre parcel, so a dot marks an area, not a house.

How deep wells have been drilled, decade by decade

Each line hangs from the ground to the median depth of household wells completed that decade; the shaded band is the middle half. Wells drilled later are not the same wells, so a deeper decade can mean falling water, new homes on higher or drier ground, or deeper aquifers being permitted. It is a record of what was drilled, not a single cause.

Mining Legacy

Mining has been part of Park County since the gold rush. The Fairplay Mining District has 18,081 total claims on record (729 active, 17,352 closed) and at least 8 documented mines. Massive tailings piles line the Middle Fork of the South Platte River.

Mining operations disturb the natural geology and can mobilize heavy metals — lead, arsenic, cadmium, zinc — into groundwater. Tailings piles leach contaminants for decades or centuries after mining stops. Acid mine drainage changes water chemistry in ways that increase metal solubility.

A USGS study of ground-water quality in the vicinity of Fairplay and Alma (2002) specifically examined alluvial and sedimentary-rock aquifers in the area to assess the impact of this mining legacy on water quality.

PFAS: A Modern Contamination

In a more recent development, CDPHE tested 14 private wells in the Burland Ranchettes community in Park County. The results were concerning: PFAS levels exceeded the EPA's proposed maximum contaminant level in 8 of the 14 wells — more than half.

PFAS ("forever chemicals") are synthetic compounds that don't break down in the environment. They've been linked to cancer, immune system effects, and developmental problems. Sources can include firefighting foam, landfills, and industrial discharges.

Private wells are not regulated for PFAS, but the EPA has proposed an MCL of 4 parts per trillion for PFOA and PFOS. If you're in an area with potential PFAS sources, testing is important.

Mountain Well Challenges

Much of Park County is underlain by the same fractured crystalline bedrock found throughout the Front Range mountains. Wells in these formations face the standard mountain challenges: low yield, seasonal variation, and uranium/radon from granitic rocks.

The alluvial aquifers along valley floors (including the area around Fairplay) can produce more water but are more vulnerable to surface contamination — including contamination from mining operations and the Fairplay landfill, which has documented leaching issues.

Testing Recommendations

Park County well owners should test for:

Heavy metals panel — lead, arsenic, cadmium, zinc, copper, especially if near mining areas
Radon and uranium — from the granitic geology
PFAS — if in or near Burland Ranchettes or other areas with potential sources
Bacteria and nitrates — annual basics

Contact Park County Environmental Health at (719) 836-4267 or CDPHE at (303) 692-3039 for testing guidance. See our testing guide for labs.

Every well is different. Two wells on the same street can produce completely different water. The data on this page reflects documented conditions in the Park County area, but the only way to know what's in your water is to test it.

Sources

USGS Fact Sheet 2004-3065 — Ground-Water Quality of Alluvial and Sedimentary-Rock Aquifers, Fairplay and Alma, Park County
CDPHE — Burland Ranchettes PFAS Testing Results
Park County Environmental Health — Well and Drinking Water Safety
Mindat.org — Fairplay Mining District Records